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								        Define Unit testing, Integration testing, Regression testing.Unit testing:
  - Unit testing ensures that each piece of code works correctly.  - It is a software development process where the smallest testable parts of an application known as units are individually and independently scrutinized for proper operation. - It is automated and can also be done manually.
  Integration testing:
  - Integration testing ensures each module work together without errors. - It is a phase in software testing where the individual software modules are combined and tested as a group. - It generally occurs after the unit testing and before the validation testing.
  Regression test:
  - Regression test ensures new code did not break previously working code. - It is a type of software testing which seeks to uncover the new software bugs or the regressions in the existing and the non-functional areas of a system where some of the changes have been made in the enhancements, patches or the configuration changes.
								          
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